This invention relates to room temperature curable compositions, and more particularly, to room temperature curable compositions of the condensation curing type having fast curing and deep curing capabilities.
Nowadays elastic sealing materials are widely employed in a variety of applications, typically in buildings and automobiles. On use, sealing materials are filled in joints and gaps between various members for forming water- and gas-tight seals. The sealing materials are therefore required, after being filled in joints or around window frames, to quickly cure and form a firm bond to various substrates, typically of inorganic materials such as glass, ceramics, metals, cement and mortar and organic materials such as plastics.
Room temperature fast curable saturated hydrocarbon polymer compositions are known effective as the sealing material. For improving the adhesion of such compositions, a primer composition and a bonding method have been proposed as disclosed in JP-A 11-209701. However, these compositions are not satisfactory in curing capability and a need exists for further improvements in curing performance.
An object of the invention is to provide a room temperature fast curable composition of the condensation curing type which is improved in curability, especially in fast curing at room temperature and curing to depth.
It has been found that blending (A) a saturated hydrocarbon polymer having a number average molecular weight in the range of 500 to 50,000 and bearing at least two hydrolyzable silyl groups at an end of the backbone and/or an end of a side chain per molecule, with (B) an organic compound having at least one Cxe2x95x90O group in a molecule, and (C) an organic compound having at least one NH2 group in a molecule, the Cxe2x95x90O group in component (B) and the NH2 group in component (C) being selected so as to be reactive with each other, leads to a room temperature fast curable composition of the condensation curing type which is improved in both fast curing at room temperature and curing to depth.
Room temperature fast curable organopolysiloxane compositions of the condensation curing type known in the art include compositions of one part type comprising a both end hydroxy-terminated organopolysiloxane as a base polymer and a crosslinking agent in an amount minimized so as to increase the rate of crosslinking through hydrolysis, and compositions of two part type wherein a both end hydroxy-terminated organopolysiloxane as a base polymer and a crosslinking agent are separately packed.
The compositions of one part type, however, are not regarded as fast curing since they merely have a high curing rate from the surface and require a certain time for deep curing. By contrast, the compositions of two part type are relatively fast in depth curing, but are difficult to handle on account of a mixing ratio of the two parts departing from 1:1 and thus inapplicable to an automatic mixing dispenser. In order to drive complete curing to depths, the quantity of hydroxyl at both ends of organopolysiloxane or polyoxyalkylene polymer and the quantity of crosslinking agent added must be strictly controlled, or water must be further added as a deep curing agent.
On the other hand, organopolysiloxane compositions of the addition curing type are efficient to work since the two parts are mixed in a ratio of 1:1. However, the working environment is limited since a heating oven is generally necessary for curing and the curing catalyst can be poisoned in the presence of an addition poison.
To solve these problems, we proposed in JP-A 5-279570 a composition comprising a diorganopolysiloxane or polyoxyalkylene as a base polymer, an organic compound having a double bond in the form of a Cxe2x95x90O group and an organic compound having a NH2 group wherein instead of directly adding water necessary for condensation curing, water is generated within the composition by reaction between the organic compounds. The composition is improved in deep curing and fast curing properties. However, the silicone base compositions are less stain resistant as the sealing agent, and the polyether base compositions are insufficient in durability and curability. Where saturated hydrocarbon polymers are used, stain resistance is good, but curability is very low as compared with silicone base compositions.
Continuing investigations, we have found that in the composition comprising the saturated hydrocarbon polymer (A), organic compound (B) and organic compound (C), crosslinking reaction takes place between a hydrolyzable silyl group at an end of the backbone and/or a side chain of the saturated hydrocarbon polymer (A) and air-borne moisture, and in parallel therewith, dehydration condensation reaction takes place between compound (B) and compound (C) according to the following scheme (I):
R2Cxe2x95x90O+H2NRxe2x80x2xe2x86x92R2Cxe2x95x90NRxe2x80x2+H2Oxe2x80x83xe2x80x83(I)
wherein R and Rxe2x80x2 are organic groups, allowing crosslinking reaction to proceed with the water generated in depth within the composition as well. As a result, the inventive composition is improved in fast curing and also drastically improved in deep curing. Additionally, the composition has good stain resistance and durability.
This also overcomes the problems of water separation and a decline of workability due to increased thixotropy as found in prior art compositions wherein water is added as a deep curing agent. The present invention is predicated on these findings.
Accordingly, the invention provides a room temperature curable composition comprising (A) 100 parts by weight of a saturated hydrocarbon polymer having a number average molecular weight in the range of 500 to 50,000 and bearing at least two hydrolyzable silyl groups at an end of the backbone and/or an end of a side chain per molecule, (B) an organic compound having at least one Cxe2x95x90O group in a molecule, in such an amount as to give 0.001 to 1 mol of the Cxe2x95x90O group per 100 parts by weight of polymer (A), and (C) an organic compound having at least one NH2 group in a molecule, in such an amount as to give 0.001 to 1 mol of the NH2 group per 100 parts by weight of polymer (A), components (B) and (C) being selected such that the Cxe2x95x90O and NH2 groups in the respective components are reactive with each other.
Component (A)
Component (A) is a base polymer. Any of saturated hydrocarbon polymers excluding polyether polymers is used. The saturated hydrocarbon polymer must have at least two hydrolyzable silyl groups at an end of the backbone and/or an end of a side chain per molecule. Owing to the presence of hydrolyzable silyl groups, the base polymer undergoes hydrolysis and polycondensation in the presence of air-borne moisture and water generated by reaction of components (B) and (C) to be described later, forming a cured product of rubber elastomer.
The hydrolyzable silyl group is defined as a silicon atom having at least one hydrolyzable group attached thereto and represented by the following formula. 
Herein X is a hydrolyzable group, p is an integer of 1 to 3, and R1 is a substituted or unsubstituted monovalent hydrocarbon group. Examples of the hydrolyzable group (X) include carboxyl, ketoxime, alkoxy, alkenoxy, amino, aminoxy, and amide groups. The hydrolyzable group attached to a single silicon atom is not limited to one, and two or three hydrolyzable groups may be attached to a common silicon atom. Another organic group or groups may, of course, be attached to the silicon atom having the hydrolyzable group or groups attached thereto. Examples of the organic groups (R1) include alkyl groups such as methyl, ethyl and propyl, cycloalkyl groups such as cyclohexyl, alkenyl groups such as vinyl and allyl, aryl groups such as phenyl and tolyl, and substituted ones of the foregoing groups in which some hydrogen atoms are replaced by halogen atoms or the like, such as chloromethyl and 3,3,3-trifluoropropyl.
The base polymer (A) should have a number average molecular weight in the range of 500 to 50,000. Outside the range, there arise inconvenient problems including difficulty to form a cured rubber having satisfactory properties and inefficient working.
The base polymer is not critical as long as it is selected from saturated hydrocarbon polymers such as ethylene polymers, propylene polymers and isobutylene polymers. Preferably the polymer (A) has in its backbone a structure of the following general formula (1): 
wherein R, which may be the same or different, is a substituted or unsubstituted monovalent hydrocarbon group, m and n are positive integers such that the polymer has a number average molecular weight in the range of 500 to 50,000. More preferably the polymer (A) has the following general formula (2): 
wherein R and R1, which may be the same or different, are substituted or unsubstituted monovalent hydrocarbon groups, X is a hydrolyzable group as defined above, p is an integer of 1 to 3, preferably 2 or 3, and m and n are positive integers as defined above. Examples of the group R are the same as the organic groups (R1), other than the hydrolyzable groups, enumerated above in connection with the hydrolyzable silyl groups. Letters m and n are such that the unsaturated hydrocarbon polymer has a number average molecular weight within the above-defined range.
Component (B)
Component (B) is an organic compound having at least one Cxe2x95x90O group in a molecule, which reacts with an organic compound having at least one NH2 group in a molecule as component (C) to produce water serving as a curing agent in the deep interior of the composition.
Any desired organic compound may be used as long as it has a carbonyl (Cxe2x95x90O) group capable of reaction as shown by scheme (I). Examples include ketones such as acetone, methyl ethyl ketone, and acetophenone, esters such as ethyl acetate, butyl acetate, methyl propionate, ethyl acrylate and butyrolactone, amides such as dimethylformamide, diethylacetamide, and butyrolactam, carboxylic acids such as acetic acid, propionic acid, and benzoic acid, silane coupling agents having the foregoing as a functional group, and oligomers and polymers having Cxe2x95x90O groups. Among others, ketones are especially preferred. Preferred from the standpoint of steric hindrance during reaction with component (C) is a compound in which the carbon atom at xcex1-position relative to the carbonyl group is primary, secondary or a part of an aromatic ring. If the carbon atom at xcex1-position is a tertiary carbon atom as usual, reactivity with an amino group may be low, with a failure to achieve the desired cure. These compounds may be used alone or in admixture of two or more.
The amount of component (B) blended is to give 0.001 to 1 mol and preferably 0.01 to 0.1 mol of the carbonyl (Cxe2x95x90O) group per 100 parts by weight of component (A). Less amounts of component (B) fail to achieve satisfactory deep curing whereas excessive amounts of component (B) result in cured elastomers which will not exhibit the desired physical properties.
Component (C)
Component (C) is an organic compound having at least one NH2 group, which reacts with component (B) to produce water serving as a curing agent in the deep interior of the composition as described above.
Any desired organic compound may be used as long as it has a reactive amino (NH2) group capable of reaction as shown by scheme (I). Examples include amines such as methylamine, ethylamine, butylamine, ethylenediamine, and aniline; silane coupling agents having NH2 as a functional group such as xcex3-aminopropyltriethoxysilane, and oligomers and polymers having NH2 groups. From the standpoint of steric hindrance during reaction with component (B), component (C) is preferably an organic compound in which the carbon atom at xcex1-position relative to the amino group is primary, secondary or a part of an aromatic ring. If the carbon atom at xcex1-position is a tertiary carbon atom as usual, then the amino group in component (C) may become less reactive with the carbonyl group in component (B), sometimes failing to achieve the desired effect. These compounds may be used alone or in admixture of two or more.
The amount of component (C) blended is to give 0.001 to 1 mol and preferably 0.01 to 0.1 mol of the amino (NH2) group per 100 parts by weight of component (A). Less amounts of component (C) fail to achieve satisfactory deep curing whereas excessive amounts of component (C) result in cured elastomers which will not exhibit the desired physical properties.
Components (B) and (C) are preferably blended such that the molar ratio of Cxe2x95x90O to NH2 may range from 1/10 to 10/1, especially from 1/5 to 5/1.
Other Components
In addition to the foregoing essential components (A) to (C), various other addenda may be added to the composition of the invention insofar as they do not adversely affect the fast curing and deep curing at room temperature. Since it is crucial for the invention that components (B) and (C) react to form water serving as a deep curing agent as seen from scheme (I), organic compounds are, of course, selected for components (B) and (C) so that this type of reaction may instantaneously take place, and various addenda which are optional must be selected so as not to inhibit the formation of water.
As a typical addendum, it is preferred to blend in the composition a hydrocarbon plasticizer (D) such as paraffinic process oil. The hydrocarbon plasticizer is preferably blended in amounts of 5 to 200 parts, especially 10 to 100 parts by weight per 100 parts by weight of component (A).
Other exemplary addenda include condensation catalysts such as organic tin esters, organic titanate esters, tetra-methylguanidylpropyltrimethoxysilane; storage stabilizers such as methyltrimethoxysilane, methyltripropenoxysilane, vinyltributanoximesilane and methyltriacetoxysilane; and reinforcing fillers such as fumed silica, precipitated silica, quartz flour, titanium oxide, aluminum oxide, carbon powder, bentonite, wood chips, pulp, cotton chips, asbestos, glass fibers, carbon fibers, mica, ground walnut shell, ground chaff, graphite, diatomaceous earth, terra abla, silicic anhydride, carbon black, calcium carbonate, clay, talc, magnesium carbonate, aluminum fine powder, print powder and zinc powder. Of these fillers, precipitated silica, fumed silica, carbon black, calcium carbonate, titanium oxide and talc are preferred. Also included are radical inhibitors and antiozonants, for example, phenolic antioxidants, aromatic amine antioxidants, sulfurous hydroperoxide decomposers, phosphorous hydroperoxide decomposers, benzotriazole UV absorbers, salicylate UV absorbers, benzophenone UV absorbers, hindered amine photo-stabilizers, and nickel photo-stabilizers. Further included are fibrous fillers such as asbestos, glass fibers and organic fibers; coloring agents such as pigments and dyes; heat resistance modifiers such as red iron oxide and cerium oxide; freeze resistance modifiers; dehydrating agents; rust-preventing agents; tackifiers such as xcex3-glycidoxy-propyltriethoxysilane; liquid reinforcing agents such as a network polysiloxane consisting of triorganosiloxy units and SiO2 units; metal inactivating agents, lubricants, pigments and foaming agents. These addenda may be used in conventional amounts.
Curable Composition
The composition of the invention can be formulated as a room temperature fast curable composition of one part type by uniformly mixing predetermined amounts of components (A) to (C) and optional components and in a dry or anhydrous atmosphere if necessary. To insure shelf stability, component (B) or (C) may be microcapsulated prior to blending into a room temperature fast curable composition of one part type.
Alternatively, the composition of the invention can be formulated as a two part type wherein the two parts are mixed on use. In one example, one part is composed of components (A) and (B) and the other part is composed of components (A) and (C). In these examples, the two parts can be mixed in a ratio of 1:1.
The inventive composition thus obtained will cure in the presence of moisture in air. During the process, water forms at depths to induce curing thereat. Both curing from the surface and curing at depths take place at the same time, facilitating fast curing and deep curing.
When the inventive composition is formulated as a two part package whereupon the two parts are mixed on use, the mixing step is very easy on account of the mixing ratio of 1:1. Furthermore, the respective components are readily available. Thus the invention is of great worth in practical application.
Because of the fast curing and deep curing advantages as well as stain resistance and durability, the inventive composition is very suitable as automobile oil seal material and also useful as sealing agents and potting agents in electric and electronic applications where simple, efficient steps are strongly demanded for manufacture.